This invention relates to an electron storage ring apparatus and, in particular, to an improvement of a bending magnet unit provided to the electron storage ring apparatus. The electron storage ring apparatus of the type is suitable for an apparatus for generating synchrotron radiation light. The synchrotron radiation light will be called SR light hereinunder.
Generally, the electron storage ring apparatus of the type comprises a vacuum chamber for defining an electron beam path of a race track type. Specifically, the vacuum chamber has two linear portions parallel to each other and two arc-shaped portions connecting the two linear portions at the both sides thereof. Each of the arc-shaped portions at the both sides Is provided with a bending magnet unit. The bending magnet unit comprises an iron yoke (hereinunder abbreviated to yoke) and a coil and deflects the electron beam along an orbit of an arc shape. In the vicinity of the electron storage ring apparatus, an injection accelerator for generating and accelerating electrons is arranged. The linear portions comprise an inflector electromagnet for introducing the electrons from the injection accelerator into the vacuum chamber and a plurality of focussing electromagnets.
By the electron storage ring apparatus, the electrons introduced into the vacuum chamber are circulated along an orbit of a race track type, and stored therein. While the electron beam is circulated, the SR light is generated in a tangential direction with the movement of the electron beam in the arc-shaped portion, namely, in the bending magnet unit. The SR light is extracted at a plurality of portions in the arc-shaped portion. Accordingly, the bending magnet unit is provided with a plurality of extraction paths for extracting the SR light.
The electron storage ring apparatus of the type is required to increase as much as possible the strength of a magnetic field generated by the bending magnet unit. For this purpose, it is necessary to widen the sectional area of the yoke. On the other hand, the light strength per unit area is inversely proportional to the square of the length from a light source. Accordingly, it is preferable that each of the plurality of the extraction paths is as short as possible. However, this means that the extraction path for extracting the SR light becomes longer.
Incidentally, the electron beam circulating along the orbit deviates from the orbit for reasons of collision with corpuscles within the vacuum chamber and becomes extinct gradually for reasons of collision with a wall of the vacuum chamber. On collision with the wall of the vacuum chamber, the electrons generate radiation such as .gamma. rays and neutron rays. Since the probability of electron being lost within the bending magnet unit is high, radiation is mostly generated within the bending magnet unit. Fortunately, the bending magnet unit has an outer peripheral yoke which is thick, so that it is possible to shield the radiation to some extent. However, the bending magnet unit is not provided with a yoke at an inlet side and an outlet side of the electron beam. Especially, in a conventional bending magnet unit, there is no shielding member for shielding the radiation from the outlet side of the electron beam, so that it is necessary to provide the shielding member for shielding the radiation outside the electron storage ring apparatus.